The direct hydrogenation of carboxylic acids to the corresponding alcohols is a relatively difficult and inefficient reaction. One large scale method of producing alcohols from carboxylic acids is by an indirect method employing metallic sodium reduction of an ester derivative of the carboxylic acid corresponding to the desired alcohol product.
U.S. Pat. No. 1,839,974 describes a process for direct conversion of carboxylic acids to alcohols in the presence of a heterogeneous metal chromite catalyst at a relatively high temperature.
U.S. Pat. No. 2,607,807 describes a process for reduction of carboxylic acids to the corresponding alcohols with hydrogen in the presence of a solid phase ruthenium-containing hydrogenation catalyst.
A Journal of Organometallic Chemistry, 188, 109 (1980) publication describes homogeneous catalytic hydrogenation of free carboxylic acids in the presence of cluster ruthenium carbonyl hydrides. Acetic acid is reduced at 180.degree. C. to ethyl acetate with a conversion of 18.7% in 48 hours. At 200.degree. C., in 48 hours the conversion is 44.5% to ethyl acetate/ethanol (72/28).
Other prior art of interest with respect to the present invention are processes which employ heterogeneous or homogeneous ruthenium-containing catalysts in the presence of hydrogen and/or carbon monoxide to produce alcohols and esters, and the like, such as U.S. Pat. Nos. 3,285,948; 3,935,284; 4,189,441; 4,269,784; 4,323,513; and 4,339,545.
There is continuing research effort to develop improved catalysts and processes for conversion of carboxylic acids to the corresponding alcohols.
Accordingly, it is an object of this invention to provide an improved process for direct hydrogenation of a carboxylic acid to the corresponding alcohol product and/or the carboxylic acid ester of the corresponding alcohol product.
It is a further object of this invention to provide a homogeneous hydrogenation catalyst composition comprising soluble ruthenium compound and Lewis Acid metal halide components in a liquid phase medium.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.